The lighthouse was not originally painted but, by 1814,
Stevenson noticed it was getting so discoloured that from
then on he had it painted on a regular basis.

In 1842, the complete lighting apparatus (reflectors, lamps,
and revolving machinery) was removed and shipped to Newfoundland,
and for years it illuminated Bonavista Lighthouse
until after 1872. The new mechanism in the Bell Rock had
fully equalised light beams. About 1877, paraffin oil replaced
the use of spermaceti oil.

A view of the kitchen in the
tower

From the time the light was first lit, until Saturday,
April 5, 1890, the Bell Rock had never failed. In 1890,
a tonite-explosive fog signal was installed. Tonite
is a blasting explosive made from guncotton and barium nitrate.
On that particular evening, this explosive went off prematurely,
which considerably damaged the light room. It took until
Sunday, April 13, before the light was repaired and operational
again.

Major alterations

In 1902, the whole of the top part of the lighthouse was
removed and the entire lighting mechanism taken out. The
new dome and lantern were installed and the lighthouse continued
to emit red and white beams from one of the finest lenticular
apparatuses then made. The lenses were equiangular glass
prisms, which had a focal distance of 1330mm. In this mechanism
there was a centrally fixed incandescent paraffin lamp around
which revolved the powerful lenses.

During these alterations, the two fog warning bells, which
were now obsolete, were removed. One of these five hundredweight
bells was gifted to the museum and when the old Arbroath
Museum was given new life and rehoused in the Signal
Tower complex, the fog bell was given pride of place
in the Bell Rock room, where it can still be seen today.
The new light flashed red and white every 60 seconds.

The changes of 1902 were full documented in the 1901 June edition of "The Engineer" - all of which has been transcribed below:
___________________________________________

From: “The Engineer”- June 7, 1901 – pp. 585/6

GLASGOW INTERNATIONAL EXHIBITION

No. VIII

"On the slopes of Gilmorhill, almost below the Glasgow University, and at an altitude which favourably lends itself to the efficient display of their capabilities, are placed two light towers, one of which contains a search-light projector of the Schuckert manufacture. This projector has a glass parabolic mirror 900 mm. in diameter, with iris screen, double disperser, and Venetian blind signalling apparatus, such as is fitted on men-of-war.

"The second tower referred to is more of the lighthouse order. In fact, the lantern, machine, lamps, and apparatus which constitute the exhibit are intended for the Bell Rock Lighthouse. These have been prepared mainly, and will be finally fitted up at this well-known lighthouse by Steven and Struthers, of Anderston Brass Foundry, Glasgow. The optical apparatus, which is the most interesting and novel feature about the exhibit, has been constructed by Lepante et Cie., of Paris; and the whole of the work is from designs by Messrs. D. and C. Stevensons, Edinburgh, the engineers to the Commissioners of the the Northern Lighthouse Board, &c.

"The Bell Rock Lighthouse is situated twelve miles from Arbroath, and stands on a dangerous reef which is little more than awash at low water, and covered to a depth of 10ft. at high water. The house was lighted for the first time in 1811, having taken four years to construct; and considering the position, and especially the period at which it was erected – when there were no steamers nor steam cranes available – it is a notable work. It is now the oldest existing rock lighthouse tower in Great Britain. The tower and apparatus were designed by Robert Stevenson, engineer to the Commissioners of Northern Lighthouses, and executed under his direct superintendence. With striking prescience, Stevenson seems to have realised the forces to which it would be exposed, proportioned his tower accordingly and introduced improvements in construction. This almost century-old lighthouse shows no signs of such weakness as has appeared in other towers – Smeaton's Eddystone, the Bishop Rock, &c. – involving their reconstruction. Although the tower is still quite equal to its purpose, the lantern and machine – which are the original ones, and are therefore, about 90 years old – show signs of requiring renewal. Both the lantern and machine and the apparatus are antiquated, and the light is too weak in power for a place of such maritime importance.

"The Commissioners accordingly resolved some time ago to renew these parts of the installation, and they are exhibited at Glasgow with the consent of the Commissioners.

The original diagram in the "The Enineer" magazine of 1901

"The optical apparatus has been designed specially by Messrs. Stevenson to suit the peculiar circumstances. The character of the light had to be maintained as it exists at present, viz., a red and white flash alternately, and of a maximum power consistent with one of the beams being red. It is somewhat of the bivalve type, but differs largely from anything yet constructed. It is a combination of two orders – hyper-radiant and first order. The white flash consists of 40 deg. of a hyper-radiant, the light from which is supplemented by back prisms of a size never before attempted. The red flash consists of 40 deg. of hyper-radiant, the light being intensified by totally reflecting prisms subtending 145 deg. Seeing a large portion of the light is lost by the red glass shades which naturally so far abstract a portion of the rays by absorption, the red flash is further intensified by dioptric mirrors of the best type.

"Although the glass work has been made in Paris the design is not French, but is, as has already been stated, but D. and C. Stevenson themselves, and it is worthy of note that with the exception of the totally reflecting prisms of the first-order portion, not one of the elements of the apparatus is of Fresnel's design.

"The flash of the new Bell Rock light will be about 112,000 candle-power, and is thus about five times the power of the most powerful red light on the French coast. The profiles of the whole prisms are designed for an index of refraction of 1-53, and the glass is set in a strong gun-metal framing. The whole face of glass through which the parallel rays from the burner are sent presents a surface of no less than 9 ft. by 9 ft., or 81 square feet of local opening.

"The apparatus – of which we give an illustration – stands on a cast iron table, which is made to revolve on conical steel rollers with ball bearings, between steel rings by a circular rack and pinion, driven by a clock machine. Antifriction roller bushes and ball bearing bushes are used in the construction of the different *journals. The fly-shaft makes 200 revolutions per minute, and absolute regularity of the machine will be attained when fitted at the lighthouse by means of the governing fans. The burners are six-wick patent Doty burners, and will be supplied with paraffin oil forced up by a pump driven off the main gear of the revolving machine.

"The apparatus and machine are enclosed in a lantern 13 ft. 6 in. diameter, which will be erected on the tower at the Bell Rock after the existing lantern has been removed. The lantern is sixteen-sided, the sash frames and astragals, which are triangularly made, and thus of the strongest form, are of gun-metal of such a proportion of parts as to attain a strength of 16 tons per square inch with an extension of at least 6 per cent. The frames are glazed with polished mirror plate glass; the dome is of sheet copper, of a spherical shape, surmounted by a ventilator to secure a proper draught and exclude the severest storm.

"The lightning conductor is ¾ in. diameter, and will be connected to the existing lightning rods of the Bell Rock. The Bell Rock tower through Stevenson's forethought was protected by a lightning rod inside as well as outside, so that all metallic bodies were in metallic connection. A somewhat similar arrangement was proposed by Faraday in 1844 for the Eddystone Lighthouse, and it would seem that the best electrical knowledge of the present day has not led to the suggestion of a better escape from one of the greatest dangers our lighthouse towers are subjected to.

"The fog signalling arrangement at the Bell rock will be maintained as at present, being an explosive signal of **tonite fired by an electrical battery, designed so that the signal cannot be fired until the charge is raised to the top of the lantern."

* journal – (mech,) that part of a shaft or axle which rests on the bearings.
** tonite – blasting explosive made from guncotton and barium nitrate.
____________________________________

Modernisation programme

In 1964, the Bell Rock again underwent major alterations.
This modernisation had a dual purpose: to install
a more efficient light mechanism, and to improve the living
conditions of the keepers, as there had been little change
within the tower since it was built. One of the panel of this (1964) dioptric lens is shown here. It was presented by the NLB in the first instance to the Old Kirk, in Arbroath; it was later moved to the Signal Tower Museum in 2004.

A single panel from the 1902 Bell Rock Lighthouse upgrade,
which is now on display in the Signal Tower Museum.

At this time, the Chicken Rock Lighthouse, a rock-station
off the coast of the Isle of Man built by David and Thomas
Stevenson, was being automated, and the first order, single-flashing
apparatus became available. It was decided to use these
eight beautiful panels of lenses mounted on a twin motor
pedestal as the new Bell Rock light. These lenses revolve
at 2 r.p.m. and show a single white light every three seconds
that could be seen for up to 28 miles. A 3500-watt electric
light bulb, mounted on a lampchanger, with a spare bulb
beside it which would automatically swing into position
should the primary bulb fail, was the source of illumination
and the candle power emitted was 1,900,000. An emergency
light was placed on the lantern dome, operated from standby
batteries, to be used in case of complete failure of the
main light.

The new layout after the 1964
alteration

Electrical generators were installed to provide power
for the light and also for domestic needs. Twin 10.5 KVA
diesel generators were set up in one apartment, with
a 5 KVA unit, known affectionately as “Wee Knockie”, on
the floor above.

To alleviate the problems of supplying the Bell Rock with
fuel and water, etc., especially in winter, it was
decided to excavate into the solid sandstone base of the
lighthouse to provide a 1,100-gallon tank for fuel oil.
This was in addition to the purpose built tanks, fitted
to the outside of the cast-iron murette, which held 1200
gallons. This was enough to last 7 or even 8 months. Storage
of fresh water was increased from 260 gallons to
690 gallons using storage tanks in the lightroom and a tank
in the storeroom below. A salt-water evaporator was
also installed but in practice it was found to use too much
fuel, and it was used only in an emergency.

The fog signals were also changed, as the Tonite system
was now obsolete. Three tyfon devices were installed
round the lower lantern walkway. This mechanism uses compressed
air to produce sound on a resonator. It is electrically
operated and gives a single blast two seconds long every
minute. The rooms in the lighthouse were switched round
and the order from top to bottom was as follows: The Light-room;
Control-room; Living room; Bedrooms; Store Room; Upper Engine
Room; Lower Engine Room; Access Shaft; Entrance. The living-room/kitchen
was moved to immediately below the old light-room and, instead
of using coal as fuel, cooking was now done by gas. The
old light-room had the optical apparatus installed in its
upper level, and the sophisticated radio controlled machinery
was installed immediately below the light mechanism.

The Bell Rock acted as a coastal weather recording station
for the Meteorological Office, making hourly weather reports
to Leuchars. Recently this has been taken over by St Abb’s
Lighthouse. Eventually, in the control room, an exercise
bicycle was added to allow the keepers some healthy exercise
as you couldn’t walk far on the Rock. The bedrooms were
completely refurbished with three bunks in tiers, each in
its own tiny compartment. Electric power brought television,
which was a great bonus to keepers living in such isolation.
The original stone spiral staircase leading up to the first
room was also taken out. This allowed the construction of
an additional half-floor where a salt-water toilet was installed.

The Bell Rock lighthouse still uses the system of gratings
round the rock surface to provide level walkways. In 1975
a helipad was constructed although it can only be
used at low water and is always dependent on the wind and
weather being suitable. Radar beacons (or Racons) were installed.
Continuing the tradition of keeping abreast of innovative
technology, the Bell Rock has once again gone through a
period of major change. This oldest existing rock lighthouse
in Britain has become fully automatic. During early
summer of 1987 the complete light mechanism was once again
removed. In July of that year the Bell Rock was lit by a
temporary light, whilst the new light mechanism was being
installed.

The Automatic Bell Rock Lighthouse

The lighthouse was de-manned on the 26th October
1988. A Dalen optic was installed, replacing the existing
electric light of 1964. This type of light, named after
its Swedish inventor, uses pressure from dissolved acetylene
gas to revolve the lens before passing to a mantle type
of burner. The flash is white - every 5 seconds - and has
a nominal range of 18 miles. Remote electronic monitoring
takes place from the Northern Lighthouse Board Headquarters
in Edinburgh via Fifeness Lighthouse. Maintenance is carried
out annually. There are no fog signals at the Bell Rock
now, and radar beacons (Racons) continue to be used. These
are triggered by radar on vessels, giving a range and bearing
from the lighthouse which is displayed on the ships’ or
boats’ radar screen. This type of signal is vastly superior
to what had gone before, as it is totally unaffected by
weather conditions.

At the end of 1999 a new round of changes began at the
Bell. This refurbishment means that the Bell, in effect,
is now eco-friendly. The light, once powered by acetylene
gas, has been removed and the optic is now powered from
batteries charged by solar panels, helped along during the
long winter months by generators. The work started by installing
new batteries in the battery room; followed by the re-installation
of new generators. It is interesting to note, that when
the light was de-manned, the generator sets were removed
and the room they occupied was converted to a gas room which
was used to house the acetylene cylinders (which in turn
powered the optic). The present arrangement removed the
gas cylinders, and the room has been converted back to an
engine room, which now houses two 10kW generators. As they
say: Plus ça change, plus c'est la même chose. (The
more things change the more they remain the same).

For a full update of the latest changes at the Bell
Rock - see Automation